IFMU,
Please view the first picture in your link on post #483 and envision that the slow turning rotors represent wings. The X2 pusher prop is totally below these 'wings'.
IMHO, the propeller is removing some of the lift from under a portion of these 'wings'. This removal is by; physical removal, and/or by causing the the velocity on the wing's lower surface to now exceed the velocity on it's upper surface.
Here is an example of a pusher propeller working with only a wing. These propellers are drawing most of their free-stream air from the upper surface of the wings.
Dave
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The following was to be the response to your post, until the above simple explanation came about.
For the very bored here it is.
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The use of 'ground cushion' may not have been the most appropriate example but since it was used, the following is an elaboration on it.
"Note that for operation IGE the power increases rapidly as the helicopter transitions from the hover state. This is because of the formation and the influence of flow recirculation at the leading edge of the rotor disk, which causes the rotor to experience a higher induced inflow than hover in OGE, and so power requirements will increase slightly." [Source ~ PHA Page 188]
[Source ~ RWP1 Fig. 3.11]
IMHO, the implication is that the flow recirculation causes a reduction in the pressure
(1) differential between the higher pressure below the rotor and the lower pressure above the rotor. Therefor additional power is required to maintain lift.
Perhaps the better example of the same thing is Argument #2 in the link on above post #476.
No one can argue against the fact that two closely spaced coaxial rotors require significantly more power than two distantly spaced rotors, for the same amount of thrust. In other words, the upper coaxial rotor would be more efficient if the lower rotor was not 'consuming' the stream-tube from the upper rotor.
My position is that 'consuming' a PORTION of the X2 rotor's stream-tube is also of some detriment to the lift.
Graviman, should wish to present a position, please do. However, attack the subject and not the person.
Use the language of 'English' or the language of 'Math', your choice.
Use Momentum Theory or use String Theory; but provide the supporting algorithms and define the symbols if you wish to put forth an argument.
(1) The use of the word pressure could be argued until hell freeze over. Therefore please accept this easy to understand concept.